The effects of αMSH and other POMC peptides on the various tissues are mediated by a family of specific receptors. These melanocortin (MC) receptors belong to the group of G protein-coupled receptors. Five different melanocortin receptors (MC-1 to MC-5) have been cloned. It is assumed that αMSH is an important signal for regulating various melanocyte functions. It is thought, for example, that proliferation, differentiation and cytokine production by melanocytes are influenced by αMSH.
It has also been shown that POMC gene products are able to influence immune responses and inflammatory reactions. For example, it is assumed that αMSH down-regulates several proinflammatory cytokines, while the production of the antiinflammatory cytokine IL-10 is stimulated by αMSH. This means that αMSH has an important function in the suppression of immune responses and inflammatory reactions. Several studies indicate that the immunomodulatory and antiinflammatory effects of αMSH are mediated by the C-terminal region of αMSH (amino acids 11-13: Lys-Pro-Val) because administration of the C-terminal tripeptide is sufficient to induce these effects (Catania and Lipton, 1993, Endocr. Rev. 14, 564-576; Bhardvaj et al., 1996, J. Immunol. 156, 2517-2521). WO 88/00833 discloses the use of the tripeptide Lys-Pro-Val for producing a medicament for the treatment of inflammations. The C-terminal tripeptide of αMSH has likewise been proposed as agent to prevent loss of hair (FR 2 733 421).